DUI FAQ: What’s With the Penlight?

author by Misdemeanor Clinic on Mar. 22, 2018

Criminal DUI-DWI Criminal  Misdemeanor 

Summary: An explanation of one of the field sobriety tests

During a field sobriety test, why does the officer shine a penlight into your eyes? The officer is checking for something called “horizontal gaze nystagmus.” In laymen’s terms, horizontal gaze nystagmus is an involuntary jerking of the eye that can sometimes be caused by central nervous system depressants. The movements of the eyes can be affected by even small amounts of alcohol in your bloodstream. Alcohol affects the way in which your eyes track moving objects like the officer’s penlight. When nystagmus is present, the eyes do not smoothly follow the object and instead jump from location to location and when an officer observes this and/or the nystagmus occurs sooner than 45 degrees from the center, the theory is that there is a high likelihood that there is alcohol in the system.

If you have been arrested for a DUI, it is important to have a skilled attorney on your side. Whether you’ve had multiple DUIs or this is your first offense, hiring an attorney can sometimes mean the difference between having the court impose its maximum penalty on you or having your charges dropped or reduced. Contact the Misdemeanor Clinic today, because we know that Good People Can Have Bad Days!

www.misdemeanorclinic.com

Legal Articles Additional Disclaimer

Lawyer.com is not a law firm and does not offer legal advice. Content posted on Lawyer.com is the sole responsibility of the person from whom such content originated and is not reviewed or commented on by Lawyer.com. The application of law to any set of facts is a highly specialized skill, practiced by lawyers and often dependent on jurisdiction. Content on the site of a legal nature may or may not be accurate for a particular state or jurisdiction and may largely depend on specific circumstances surrounding individual cases, which may or may not be consistent with your circumstances or may no longer be up-to-date to the extent that laws have changed since posting. Legal articles therefore are for review as general research and for use in helping to gauge a lawyer's expertise on a matter. If you are seeking specific legal advice, Lawyer.com recommends that you contact a lawyer to review your specific issues. See Lawyer.com's full Terms of Use for more information.

© 2025 LAWYER.COM INC.

Use of this website constitutes acceptance of Lawyer.com’s Terms of Use, Email, Phone, & Text Message and Privacy Policies.